Method and system for combining orthogonal transmit diversity and adaptive array techniques in a wireless communications system

ABSTRACT

In a method for producing antenna element signals for transmitting a serial traffic channel from a plurality of elements in an antenna array, data in the serial traffic channel is converted to data in two or more parallel traffic channels. Thereafter, data in the two or more parallel traffic channels are spread with different spreading codes to produce spread traffic signals. The spread traffic signals are combined to produce combined signals, which are each modified according to adaptive array weights to produce element signals. A pilot signal is then added to at least one of the element signals to produce two or more antenna element signals.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of Ser. No. 09/175,050 filed on Oct.19, 1998, now U.S. Pat. No. 6,154,485.

FIELD OF THE INVENTION

The present invention relates generally to wireless communicationsystems, and more particularly to wireless communication systems usingadaptive antenna arrays.

BACKGROUND OF THE INVENTION

Recently, wireless communication systems owners and operators have askedcommunication system designers to increase the capacity of wirelesscommunication systems. This capacity, or the ability to carry user data,is what the operators sell to the system users. Therefore, increasedcapacity means increased profitability for communication systemoperators.

One method of improving capacity is to reduce the amount of energyneeded to transmit a bit of information over the wireless air interface.Several methods of reducing the energy per bit have been proposed. Twoof these proposals include transmitting user data using adaptive antennaarrays, and transmitting data using a method of transmission known as“orthogonal transmit diversity.”

Transmitting user data with adaptive antenna arrays is a techniqueimplemented by measuring the channel characteristics and modifying thegain and phase of signals applied to each element in an antenna array inorder to create an antenna pattern that maximizes the power delivered tothe subscriber unit. One of the disadvantages of adaptive arraytechnology is the need for constant measurement and feedback of thechannel characteristics and the subsequent recalculation of the adaptivearray weights used to modify signals for each antenna element. The timeneeded to measure and compute the weights limits the speed at which theantenna pattern may be modified to compensate for a changing channel.Thus, when the subscriber travels at a higher speed, the channel changesat a rate higher than the rate of compensation in the adaptive antennaarray. Thus, the feedback loop in the adaptive array technique cannotkeep up with a quickly changing channel between the base station antennaand a higher-speed subscriber unit.

With regard to orthogonal transmit diversity, it is implemented by firstconverting a serial traffic channel into two or more parallel trafficchannels using a multiplexer. If the traffic channel is converted intotwo parallel traffic channels, the two parallel traffic channels operateat one half the rate of the serial traffic channel input into themultiplexer.

Once the data is multiplexed, each parallel traffic channel is spreadwith a different spreading code to produce two or more spread trafficsignals. These two spread traffic signals are then added together andtransmitted from either a single antenna or separately transmitted fromtwo or more separate antennas.

Some designers have proposed a communication system that switches fromadaptive antenna transmission to orthogonal transmit diversity when thefeedback required in adaptive antenna transmission begins to fail. Afirst problem with this mode switching proposal is that the receivermust be able to operate in two modes, where the adaptive array modedemodulates with one despreading code, and the orthogonal diversity modedemodulates with multiple codes despreading. Operating in two modesrequires additional complexity in the receiver.

Because it is desirable to use a single receiver structure, it has beenproposed that radio systems having orthogonal transmit diversitycapabilities always transmit with multiple codes, even when transmitdiversity is not active. Presently known transmitters using adaptivearrays presume that a single code spreads the transmitted data, which isa mode incompatible with the orthogonal transmit diversity proposal.

Another problem with the mode switching proposal is that the basestation is required to send a message which tells the mobile which modeto use. Such messaging is slow in switching modes and requiresadditional mobile station circuitry or programming to implement.

Therefore, it should be apparent that there is a need for an improvedmethod and system of transmitting and receiving a traffic channel usingtechniques from both orthogonal transmit diversity and adaptive antennaarray transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objects, and advantages thereof, willbest be understood by reference to the following detailed description ofan illustrative embodiment when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 depicts a wireless communications system in accordance with themethod and system of the present invention;

FIG. 2 a high-level flowchart illustrating the process of producingantenna element signals in accordance with the method and system of thepresent invention;

FIG. 3 is depicted a high-level flowchart illustrating the process ofdemodulating a signal in a subscriber unit wherein the signal has beentransmitted according to the present invention;

FIG. 4 depicts an alternate embodiment of an adaptive array processor inFIG. 1 in accordance with the method and system of the presentinvention;

FIG. 5 depicts yet another alternate embodiment of an adaptive arrayprocessor in accordance with the method and system of the presentinvention;

FIG. 6 depicts yet another embodiment of an adaptive array processor inaccordance with the method and system of the present invention; and

FIG. 7 there is depicts still another embodiment of an adaptive arrayprocessor in accordance with the method and system of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to FIG. 1, there is depicted wireless communicationssystem 50, which may be used to implement one embodiment of the methodand system of the present invention. Wireless communication system 50includes base transmitter 52, which transmits signals via communicationchannel 54 to subscriber unit 56. Note that FIG. 1 shows only thedownlink of a communications system that may also include an uplink forduplex operation. An uplink may also be required for providing afeedback loop for data and commands for operating the downlink in anadaptive array mode.

Base transmitter 52 includes traffic channel 58, which is typically aserial data stream source of user data. Such data may represent voicesignals or other user data, such as software, documents, images,facsimile data, or the like.

As shown, traffic channel 58 is coupled to spreading processor 60.Spreading processor 60 includes multiplexer 62, which is used to converttraffic channel 58 into two or more parallel traffic channels operatingat a data rate that is inversely proportional to the number of trafficchannels created by multiplexer 62. For example, as shown in FIG. 1,multiplexer 62 converts traffic channel 58 into two parallel trafficchannels 64 and 66, each of which operates at one half the data rate oftraffic channel 58, the input to multiplexer 62.

Parallel traffic channels 64 and 66 output by multiplexer 62 are coupledto spreaders 68 and 70, which spread the parallel traffic channels usingspreading codes W₀ and W₁, as shown. The outputs of spreading processor60 are spread traffic signals 72 and 74.

Spread traffic signals 72 and 74 are coupled to adaptive array processor76, wherein, in the embodiment shown, they are added together by summer78 to produce combined signal 80.

Combined signal 80 is coupled to the input of summer 82 for addingauxiliary pilot 84 to combined signal 80. Auxiliary pilot 84 is added sothat subscriber unit 56 may use it as a reference for demodulating thereceived signal.

The output of summer 82 is split and coupled to filters 86 and 88, whichfilter the signal according to adaptive array weights 90 and 92 toproduce element signals 94 and 96. Filters 86 and 88 may be implementedwith a zero-delay, single-tap digital filter, which is equivalent to acomplex multiplier.

Element signals 94 and 96 are coupled to pilot processor 98, which addsone or more pilot signals to element signals 94 and 96. As shown,summers 100 and 102 add element pilot signals 104 and 106, respectively,to element signals 94 and 96. Element pilot signals 104 and 106 are usedby subscriber unit 56 to estimate or measure channel characteristics ofcommunication channel 54. Such channel characteristics are shown aschannel impulse responses h₀, 108 and h₁, 110.

The output of summers 100 and 102 are antenna element signals 112 and114. These signals are modulated and amplified and coupled to antennaelements 116 and 118 of an antenna array.

With reference now to subscriber unit 56, subscriber antenna 120receives signals from antenna elements 116 and 118. Although not shownin FIG. 1, signals received by subscriber antenna 120 are down convertedand coupled to mode detector 122 and despreaders 124 and 126.Despreaders 124 and 126 despread the received signal by multiplying thesignal by spreading codes W₀ and W₁, wherein both multipliers arefollowed by an integration operation, as shown. Despread signals 128 and130, which are output from despreaders 124 and 126, are coupled tomultipliers 132 and 134. Multipliers 132 and 134 multiply despreadsignals 128 and 130 by RAKE weight g₀. and g₁, respectively.

RAKE weights g₀ and g₁ are computed by RAKE weight computers 136 and138. RAKE weight computation may be implemented by calculating thecomplex conjugate of the channel impulse response. When the adaptivearray mode is enabled, mode detector 122 sends a signal to pilotselectors 140 and 142 to select the auxiliary pilot for RAKE weightcomputers 136 and 138. The RAKE weight computers then use the auxiliarypilot to calculate the complex conjugate of the composite channelbetween each element 116 and 118 and the subscriber's antenna 120. Thiscomposite channel response includes impulse responses h₀ and h₁, asshown at reference numerals 108 and 110.

If the adaptive array mode in base transmitter 52 is not enabled, RAKEweight computers 136 and 138 use pilots P₀ and P₁ selected by pilotselectors 140 and 142 in order to compute complex conjugate impulseresponses of individual channels from elements 116 and 118, as indicatedby h₀ and h₁.

The reason for selecting different pilots for different modes ofoperation is that the auxiliary pilot is present in the signal from bothantennas 116 and 118 while the element pilots, P₀ and P₁, are onlypresent on one of the antenna elements 116 and 118.

When mode detector 122 detects that base transmitter 52 has enabled anadaptive array mode, mode detector 122 causes pilot selector 140 and 142to select the auxiliary pilot as a reference for RAKE weight computers136 and 138. When mode detector 122 detects that the adaptive array modeis not enabled, mode detector signal 144 causes pilot selectors 140 and142 to select element pilots P₀ and P₁ as the references provided toRAKE weight computers 136 and 138.

Output from multipliers 132 and 134 are coupled to demultiplexer 146. Asshown in FIG. 1, demultiplexer 146 receives two inputs and produces asingle output.

In order to support an adaptive array mode in base transmitter 52,subscriber unit 56 includes channel measurement and feedback processor149. Channel measurement and feedback processor 149 measures thecharacteristics of channels 108 and 110, which together may be referredto as a composite channel between base transmitter 52 and subscriberunit 56, and then appropriately formats messages to send back to a basereceiver. The information contained in such messages are used todetermine the operations performed in filters 86 and 88, which mayinclude calculating the values of V₀ and V₁.

The output of demultiplexer 146 is coupled to decoder 148, which decodesthe data that was originally transmitted from traffic channel 58.

With reference now to FIG. 2, there is depicted a high-level flowchartthat illustrates the process of producing antenna element signals fortransmitting a traffic channel from a plurality of elements in anantenna array in accordance with the present invention. As illustrated,the process begins at block 200, and thereafter passes to block 202wherein the process converts a serial traffic channel data into multipleparallel traffic channel data. This process may be implemented using amultiplexer, such as multiplexer 62 shown in FIG. 1. Note that the datarate of the parallel traffic channel data will be the data rate of theserial traffic channel data divided by the number of multiple paralleltraffic channels. Thus, the multiple parallel traffic channel data is atmost half the rate of the serial traffic channel data.

Next, the process spreads each parallel traffic channel data with aspreading code, as illustrated at block 204. This spreading operationmay be implemented as shown in FIG. 1 with spreaders 68 and 70. In apreferred embodiment, the spreaders use unique spreading codes, orspreading codes that are distinct from one another. Furthermore, thesespreading codes are orthogonal sequences which allow the spread data tobe recovered in a receiver.

Next, the process determines whether or not an adaptive array mode isenabled, as depicted at block 206. Preferably the adaptive array mode isenabled when reliable feedback is available from the subscriber unit,and when the antenna adaptation rate is fast enough to adapt to the rateat which the channel changes.

If the adaptive array mode is enabled, the process of the embodimentshown then combines a user pilot, which may be called an auxiliarypilot, and each parallel traffic channel data to produce combinedsignals, as illustrated at block 208. In one of the simplest embodimentsof the present invention, the combined signals are produced by splittingthe output signal of a summer, wherein the summer adds all the paralleltraffic channel data and the auxiliary pilot. Example of such summersare summers 78 and 82 in FIG. 1. In other more complicated embodimentsof the present invention, the combining may be implemented byappropriately weighting the parallel traffic channel data and adding theweighted data as shown and described in relation to FIGS. 5, 6, and 7.Such weighting and adding steps may be implemented with matrixmultiplication. (See FIG. 7 and related description.)

Although the process shown in FIG. 2 combines a user or auxiliary pilotsignal in block 208, some embodiments of the present invention may notrequire such an auxiliary pilot signal. Embodiments of communicationssystems that do not combine an auxiliary pilot signal may synthesize apilot signal in the receiver in the subscriber unit in order to providea reference for signal demodulation. For further information describingpilot signal synthesis in a subscriber unit see U.S. patent applicationSer. No. 09/107,106; filed: Jun. 30, 1998; entitled: “Method and Systemfor Transmitting and Demodulating a Communications Signal Using anAdaptive Antenna Array in a Wireless Communication System”, which isincorporated herein by reference.

Next, in the embodiment shown, the process filters the combined signalsaccording to adaptive array weights to produce element signals, asdepicted at block 210. This step of filtering may be implemented with adigital filter, which is some cases may be a one-tap, zero-delay filter,which is equivalent to a multiplier. The adaptive array weights used bythe filters are derived from measurements or estimations of the channelimpulse responses of channels from each element of the antenna array atthe base to the subscriber antenna. These array weights may becalculated as described in the above-identified referenced U.S. patentapplication Ser. No. 09/107,106; filed: Jun. 30, 1998; entitled: “Methodand System for Transmitting and Demodulating a Communications SignalUsing an Adaptive Antenna Array in a Wireless Communication System.”

After the combined signals have been filtered, the process adds anelement pilot signal to each element signal to produce antenna elementsignals, as illustrated at block 212. Each element pilot signal isdifferent from every other element pilot signal so that the channels canbe identified from the perspective of the subscriber unit. Thesubscriber unit may measure these element pilot signals to determine thechannel impulse responses of the channels between antenna elements andthe subscriber's antenna.

After adding the pilot signal, the process transmits the antenna elementsignals by modulating and amplifying the signals, and coupling suchsignals to corresponding antenna elements in the antenna array, asdepicted at block 214.

Referring again to block 206, if the adaptive antenna array mode is notenabled, the process adds element pilots to each spread parallel trafficchannel to produce antenna element signals, as illustrated at block 216.Thereafter, the process transmits the antenna element signals as shownat block 214.

Although the process is shown terminating at block 218, the process ispreferably repeated for each group of bits input to base transmitter 52from traffic channel 58. Thus, the process should be understood as acontinuous process implemented in base transmitter 52, wherein trafficchannel data is continuously received into the transmitter along withmeasurements and calculations needed to compute adaptive array weights90 and 92 in adaptive array processor 76, as shown in FIG. 1

With reference now to FIG. 3, there is depicted a high-level flowchartillustrating the process of demodulating a signal in a subscriber unitwherein the signal has been transmitted according to the presentinvention. As illustrated, the process begins at block 300 andthereafter passes to block 302 wherein the process determines whether ornot the adaptive array mode is enabled. The process may determinewhether or not the adaptive array mode is enabled by several techniques,some of which are discussed below. In the system shown in FIG. 1, modedetector 122 makes this determination.

If the adaptive array mode is enabled, the process then selects theauxiliary pilot for a demodulation reference to be used in thedemodulator in the subscriber unit, as illustrated at block 304. Theauxiliary pilot may be generated by known methods of producing asequence of coefficients, where such sequence is specified by a messageor other signaling from base transmitter 52.

If the adaptive array mode is not enabled, the process selects theelements pilots for demodulation references in the subscriber unit, asdepicted at block 306. The element pilots may be generated in a mannersimilar to the generation of the auxiliary pilot. The element pilots areknown sequences which are specified by a message or other signal frombase transmitter 52.

The steps depicted at blocks 302-306 may be implemented as shown in FIG.1 with mode detector 122 coupled to pilot selectors 140 and 142.

After a demodulation reference or references have been selected, theprocess computes RAKE weights using the selected demodulation referenceor references, as illustrated at block 308. RAKE weights are typicallythe complex conjugate of the coefficients of the channel impulseresponse with the greatest magnitude.

In FIG. 3, blocks 302-308 depict a process of computing RAKE weightswhich may be executed in parallel with the steps of decoding the signal,which are shown at blocks 310-316.

Turning now to the decoding steps, the process begins by despreading thereceived signal using two or more despreading codes, as depicted atblock 310. The number of despreading codes used is the same as thenumber of spreading codes used in spreading processor 60 in FIG. 1. Alsoshown in FIG. 1 are despreaders 124 and 126 which may be used toimplement this despreading step.

The despread signals are weighted and combined using the computed RAKEweights, as illustrated at block 312. The RAKE weights are computed asshown and described at block 308. This weighting and combining stepcompensates for the effects of the communication channel 54, throughwhich the received signal has passed.

Next, the process demultiplexes the signals, as depicted at block 314.This demultiplexing step takes two or more data inputs and combines theminto a single serial output. In FIG. 1, this process may be implementedwith demultiplexer 146, which receives two inputs and combines them intoa single output. This process may be thought of as the opposite of theprocess of multiplexing in base transmitter 52, as shown at block 202 inFIG. 2, and implemented with multiplexer 62 in FIG. 1.

The demultiplexed signal is then decoded, as illustrated at block 316.The decoding process may be implemented with commonly used errorcorrecting code decoders, including a soft decision Viterbi decoder.

The process of decoding a received signal according to the presentinvention is terminated at block 318. However, the process shown in FIG.3 is designed to be a continuous process of receiving, despreading,weighting, demultiplexing, and decoding signals from base transmitter52.

With reference now to FIG. 4, there is depicted an alternate embodimentof adaptive array processor 76 in FIG. 1. Adaptive array processor 150shown in FIG. 4 may be used in place of adaptive array processor 76 inFIG. 1. As shown, spread traffic signals 72 and 74 are input intoadaptive array processor 150. Control signal 152 indicates whether ornot the adaptive array mode is enabled in base transmitter 52. When theadaptive array mode is not enabled, switches 154 and 156 are in theupper position to send spread traffic signals 72 and 74 to the outputsof adaptive array processor 150.

If the adaptive array mode is enabled in transmitter 52, switches 154and 156 are in the lower position to couple spread traffic signals 72and 74 to summer 158, which adds the signals together. The output ofsummer 158 is coupled to summer 160 wherein an auxiliary pilot may beadded to the combined signals from summer 158.

The output of summer 160 is then split and filtered by filters 162 and164 in a manner similar to that described with reference to filters 86and 88 in FIG. 1.

Finally, the output of filters 162 and 164 are output from adaptivearray processor 150 as element signals 94 and 96. Thus, adaptive arrayprocessor 150 operates the same way as adaptive array processor 76except that the adaptive array processing may be enabled and disabled bycontrol signal 152. When adaptive array processor 150 is disabled, basetransmitter 52 operates in an orthogonal transmit diversity mode.

With reference now to FIG. 5, there is depicted yet another alternateembodiment of adaptive array processor 76. As illustrated, adaptivearray processor 166 receives spread traffic signals 72 and 74 as inputsto summers 168 and 170. Summers 168 and 170 add auxiliary pilots AUX₀and AUX₁ to spread traffic signals 72 and 74. Pilots AUX₀ and AUX₁ aredifferent because spread traffic signals 72 and 74 are not combined bysimply summing the two signals together as shown in FIGS. 1 and 4—inthis embodiment of adaptive array processor 166, spread traffic signals72 and 74 are combined by adding a portion of the signal in one path tothe signal in the other path. This portion is determined by thecoefficient a in FIG. 5. Thus, multipliers 172 and 174 divide the signalpower output by summer 168, wherein a portion of the signal powerproceeds on a path through adaptive array processor 166 to becomeelement signal 94, and another portion of the signal power output bysummer 168 proceeds along a path toward element signal 96. Statedanother way, the fraction of the signal power going to each output ofadaptive array processor 166 is determined by the value of α, wherein αvaries from 0 to the reciprocal of the square root of 2.

Similarly, multipliers 176 and 178 divide the signal power output bysummer 170 between the branches of adaptive array processor 166 thatproduce element signals 94 and 96.

Multipliers 180 and 182, which are simple implementations of filters,are used to modify the combined signals according to adaptive arrayweights to produce element signals 94 and 96. These filters operatesimilar to filters 86 and 88 in FIG. 1. As shown, these filters are zerodelay, single tap filters.

It should be noted that when the value of α is equal to 0, and adaptivearray weights V₀ and V₁ at multipliers 180 and 182 are equal to 1,adaptive array processor 166 is figured so that base transmitter 52operates in an orthogonal transmit diversity mode. In this case,adaptive array processor 166 behaves as though switches 154 and 156 inadaptive array processor 150 in FIG. 4 have been set to the upperposition to pass traffic signals 72 and 74 directly through to theoutputs of element signals 94 and 96.

If α is set equal to the reciprocal of the square root of 2, andcalculated adaptive array weights V₀ and V₁ are used in multipliers 180and 182, adaptive array processor 166 is configured so that basetransmitter 52 operates in an adaptive array mode. In thisconfiguration, adaptive array processor 166 behaves like adaptive arrayprocessor 150 with switches 154 and 156 set in the lower position tocouple spread traffic signals 72 and 74 through summer 158 and filters162 and 164.

If α is set to a value between 0 and the reciprocal of the square rootof 2, adaptive array processor 166 is configured so that basetransmitter 52 operates in a mixed mode—a mode that is not strictly anorthogonal transmit diversity mode nor an adaptive array mode. In thismixed mode base transmitter 52 exhibits characteristics of both modes.If the value of α is allowed to vary between its extremes, basetransmitter 52 may smoothly transition between orthogonal transmitdiversity mode and adaptive array mode. This smooth transition may allowbase transmitter 52 to slowly disable the adaptive array mode inproportion to the degradation of the quality of the feedback data, whichtypically degrades as the speed of the subscriber unit increases.

Because adding auxiliary pilots such as a AUX₀ and AUX₁ consumes powerthat might otherwise be used to transfer user data, not adding AUX₀ andAUX₁ in adaptive array processor 166 is a desirable goal. However, AUX₀and AUX₁ are added because they provide a demodulation reference insubscriber unit 56. Without this demodulation reference, the subscriberunit must know adaptive array weights V₀ and V₁ in order to properlydemodulate the received signal. Therefore, if AUX₀ and AUX₁ are notused, subscriber unit 56 must be able to calculate adaptive arrayweights V₀ and V₁, which may be accomplished mathematically by analyzingthe joint statistical characteristics of the signals output bydespreaders 124 and 126 in combination with the knowledge of the valueof α, which describes how spread traffic signals 72 and 74 are combined.

With reference now to FIG. 6, there is depicted yet another embodimentof adaptive array processor 76. As shown, adaptive array processor 230includes n+1 inputs, in contrast with the two inputs of adaptive arrayprocessors 76, 150 and 166. Within adaptive array processor 230 power issplit in equal portions from each of the n paths, and each split portionis added to another one of the n paths. The value of α sets the ratio ofpower in bits in other paths that are combined with the power of the bitinput to a particular path. The portions of energy split or divertedfrom an input path and combined with another path are all equal.

The values of α in adaptive array processor 230 range from zero to thereciprocal of the square root of n+1, as depicted in the range shown inFIG. 6. When α is equal to zero, adaptive array processor is configuredso that base transmitter 52 operates in an orthogonal transmit diversitymode. When α is set equal to the reciprocal of the square root of n+1,adaptive array processor 230 is configured so that base transmitter 52operates in an adaptive array mode. Therefore, when the value of α is ateither extreme, adaptive array processor 230 operates similar to ann+1—input version of adaptive array processor 150, which may be switchedbetween modes.

With reference now to FIG. 7, there is depicted still another embodimentof adaptive array processor 76. As depicted, adaptive array processor250 includes n+1 inputs for receiving spread traffic signals b₀-b_(n).The difference between adaptive array processor 250 in FIG. 7 andadaptive array processor 230 in FIG. 6 is the ability of adaptive arrayprocessor 250 to split unequal portions of signal power to combine withother signal paths in the adaptive array processor. In adaptive arrayprocessor 230 in FIG. 6 the portions of energy split or diverted from aninput path and combined with another path are all equal.

When adaptive array processor is set in an orthogonal transmit diversitymode, base transmitter 52 transmits a uniform level of power over anentire sector or antenna coverage area. When adaptive array mode isenabled, adaptive array processor 230 and base transmitter 52 transmitpower unevenly over the sector, ideally with the maximum power beingdelivered to the subscriber unit.

Because the energy split or diverted from one path for combining withanother selected path in adaptive array processor 250 may beindependently selected, and because the phase at which various paths arecombined may be individually selected, base transmitter 52 can transmitdifferent spread bits with different codes in different amounts of poweracross different directions in a sector. This mode of operation is afurther generalization of orthogonal transmit diversity and adaptiveantenna transmission.

Note that as the number of paths or branches in adaptive array processor76 increases above two paths, modification must be made in spreadingprocessor 60, pilot processor 98, and subscriber unit 56. In spreadingprocessor 60, multiplexer 62 must output n+1 branches or paths.Additional spreaders such as 68 and 70 must be added for each path. Withregard to pilot processor 98, additional summers such as 100 and 102 maybe needed for each path, along with new element pilot signals, such aselement pilot signals 104 and 106. Additional antenna elements 116 and118 may also be needed.

In subscriber unit 56, additional demodulation paths may be needed,wherein such paths include despreaders 124 and 126 and multipliers 132and 134. Demultiplexer 146 must be able to demultiplex n+1 inputs.

Also note that in the embodiment in FIG. 1, the number of spread trafficsignals 72 and 74 may or may not be equal to the number of elementsignals 94 and 96. For example, the number of spreading codes used neednot be equal to the number of elements used in the antenna array.

With regard to mode detector 122 in FIG. 1, several methods may be usedto detect whether or not the transmitter is transmitting in an adaptivearray mode or not. One simply method includes sending a message frombase transmitter 52 to subscriber unit 56. Another method that may beused is the detection of auxiliary pilot 84. For example, if theembodiment shown in FIG. 4 is used, adaptive array processor 150 adds anauxiliary pilot to element signals 94 and 96 when control signal 152places switches 154 and 156 in the lower position to enable the adaptivearray mode. When control signal 152 sets switches 154 and 156 to theupper position, an auxiliary pilot signal is not present in elementsignals 94 and 96. This would indicate to subscriber unit 56 thattransmitter 52 is operating in the orthogonal transmit diversity mode.

The foregoing description of a preferred embodiment of the invention hasbeen presented for the purpose of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Modifications or variations are possible in light of theabove teachings. The embodiment was chosen and described to provide thebest illustration of the principles of the invention and its practicalapplication, and to enable one of ordinary skill in the art to utilizethe invention in various embodiments and with various modifications asare suited to the particular use contemplated. All such modificationsand variations are within the scope of the invention as determined bythe appended claims when interpreted in accordance with the breadth towhich they are fairly, legally, and equitably entitled.

What is claimed is:
 1. A method for producing antenna element signalsfor transmitting a serial traffic channel from a plurality of elementsin an antenna array, the method comprising the steps of: converting datain the serial traffic channel to data in two or more parallel trafficchannels; spreading data in the two or more parallel traffic channelswith a spreading code to produce spread traffic signals; combining thespread traffic signals to produce combined signals by adding the spreadtraffic signals to produce an added signal and splitting the addedsignal to produce the combined signals; modifying each of the combinedsignals according to adaptive array weights to produce element signals;and adding a pilot signal to at least one of the element signals toproduce two or more antenna element signals.
 2. The method for producingantenna element signals according to claim 1 wherein the step ofspreading data further includes spreading data in each of the two ormore parallel traffic channels with unique spreading codes to producespread traffic signals.
 3. The method for producing antenna elementsignals according to claim 1 wherein the combined signals aresubstantially the same signal.
 4. A method for producing antenna elementsignals for transmitting a serial traffic channel from a plurality ofelements in an antenna array, the method comprising the steps of:converting data in the serial traffic channel to data in two or moreparallel traffic channels; spreading data in the two or more paralleltraffic channels with a spreading code to produce spread trafficsignals; combining the spread traffic signals to produce combinedsignals; filtering each of the combined signals according to adaptivearray weights to produce element signals; and adding a pilot signal toat least one of the element signals to produce two or more antennaelement signals.
 5. The method for producing antenna element signalsaccording to claim 4 wherein the step of adding a pilot signal to atleast one of the element signals to produce two or more antenna elementsignals further includes adding an element pilot signal to each of theelement signals to produce two or more antenna element signals, whereinall element pilot signals are different from every other element pilotsignal.
 6. The method for producing antenna element signals according toclaim 1 wherein the step of modifying each of the combined signalsaccording to adaptive array weights to produce element signals furtherincludes modifying each of the combined signals according to adaptivearray weights to produce element signals, wherein the adaptive arrayweights are derived from measurements of channel characteristics of achannel between the antenna array and a subscriber antenna.
 7. Awireless communication system comprising: an adaptive array transmittercomprising: a spreading processor for multiplexing and spreading trafficchannel data with multiple spreading codes to produce a plurality ofspread traffic signals; an adaptive array processor for combining theplurality of spread traffic signals in selected ratios to produce aplurality of combined signals, and weighting the plurality of combinedsignals according to adaptive array weights to produce a plurality ofelement signals; and a pilot processor for adding element pilots to eachelement signal; and a receiver comprising: a plurality of despreadersfor despreading with multiple despreading codes corresponding to themultiple spreading codes in the transmitter; a plurality of demodulatorsfor demodulating outputs of the plurality of despreaders; ademultiplexer for demultiplexing the outputs of the plurality ofdemodulators; and a decoder for decoding the output of the demultiplexerto produce received traffic channel data.